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G5RV Questions

May 1st 2012, 18:00

N3SNZ

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Hello All,

I am in the process of rebuilding my HF station. I'm considering getting a G5RV mulitband antenna since I have some really tall trees to put it up into. I "get" the theory behind the antenna and a tuner is a nessecity but beyond that, I'm confused on a few things. Here goes:

1. The G5RV is fed with twin lead ladder line and connected to coax into the tuner. Should not a balun be placed in between the ladder line and the coax?

2. I plan to use the G5RV as a sloper. How high should the terminating mast be or can I pound a post into the ground and tie it off there??

3. What is the best coaxial line to use with this and what is the best tuner to use with a G5RV for optimum results? I am building this station on a budget so a tuner for a FT-9000DX is out of the question.

Thanks and 73's

Bob Schuette, N3SNZ
May 1st 2012, 21:16

W1VT

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0

Yes, a 1:1 balun is preferred to decouple the shield of the coax and reduce shield currents and feedline radiation. A disadvantage is that ferrite baluns can burn up--but you often get a warning as evidenced by SWR drift as the ferrite heats up.

The minimum height for a G5RV depends on its application--rather low heights may work in Near Vertical Incidence Skywave applications, while the same antenna may be quite disappointing when used for working long distances. A close proximity to ground results in poor efficiency, but this isn't as important when you have a clear channel free of interference. Loud stations can keeo the channel clear during an emergency.

The best tuner is an automatic tuner located between the coax and the open wire section, but this may be too expensive for your budget. LMR-400 or 9913F7 or equivalents are typically the feedline of choice for most hams--few can justify the cost of Andrews Hardline!

Zack Lau W1VT
ARRL Senior Lab Engineer
May 4th 2012, 03:10

N3SNZ

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Thanks for the help. I have a better idea on how to go about this project.
I plan to "spud gun" the antenna in a tree that is better than 50 feet tall and slope it with the use of parachute cord to the ground.
As for feed line, I am going to research the suggestions given. I was thinking of using rg8-x which my local club uses extensively. Would this be ok to use for this application or am I asking for trouble and could I theoretically get away with using rg6 feed line? What kind of losses and SWR issues am I likely to see?
I had a cb friend try to pass off a box of rg58 coax but I get this weird "don't even think of using this stuff" feeling about it.

Decisions, decisions.

Thanks for your continued assistance and 73's.

Robert Schuette, N3SNZ
May 16th 2012, 15:14

gw0nvn

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Just to add to what's been said ( well typed in this case).
Check out what bands the G5RV is designed to work on and what the performance is. As your atu may be hiding very high transmission losses and its directional responce may not be what you want. Details are on the ARRL website (TIS) or books.

Sloping the antenna will give it some directional properties and in some cases a low angle of transmission. So good for DX. By having a number of preset anchor points in the ground on bearings to the DX locations you wish to work. It will be easy to tie off one end of the antenna support rope so the antenna is on the correct bearing. Cheaper than a beam.

Have fun 73's GW0NVN N1XIH
May 17th 2012, 16:57

W0BTU

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Check out K9YC's excellent balun and choke how-to at http://audiosystemsgroup.com/RFI-Ham.pdf . There's nothing like it anywhere. I made a common-mode choke for my old G5RV based on Jim's advice there. I believe it was 7 turns of the coax feedline (I used RG-6, 75 ohms) through four 2.4" o.d. #31 toroidal cores, right at the junction of the ladder line and the coax. Worked great. Those cores are available from mouser.com for $7 each, IIRC.

73, Mike
www.w0btu.com
http://www.w0btu.com/g5rv_antenna.html
Sep 9th 2012, 21:11

Al409991

Joined: Aug 4th 2012, 16:05
Total Topics: 0
Total Posts: 0
Does anyone know a way to contact Kerri Bickford? He makes G5RV called the true-talk which has been recomended to me and gets great reviews.Thanks Al
Sep 9th 2012, 22:34

W1VT

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Kerry's call is WA2NAN.

He has contact info on the web site qrz.com--just put his call into their search.

Zack Lau W1VT
ARRL Senior Lab Engineer

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